This invention relates generally to pulse stretching and level shifting circuitry and, more particularly, to an integrated circuit for increasing the width of a transistor-transistor logic (TTL) input pulse and making the stretched pulse available at an output as a current mode logic (CML) compatible signal.
As is well known, it is often necessary to receive electrical signals which are compatible with a first type of circuitry and convert those signals so as to be compatible with a second type of circuitry. For example, it is often necessary to convert TTL signals into signals which are compatible with CMOS circuitry and visa-versa. Similarly, a need has arisen to convert standard TTL signal pulses so as to be compatible with CML components in bubble memory interface circuits. This has, in the past, been accomplished by utilizing the time constant of an off-chip circuit to produce the required stretching. Unfortunately, the use of off-chip components presents certain disadvantages. First, there is an overall increase in a number of components required. Second, circuit accuracy may be compromised by temperature drift. Third, the use of an external circuit requires the use of a pin on the pulse stretcher and level shifter chip. In a pin limited situation, the freeing of a pin may be extremely important.